Map Tools
Calinou

Adds various special versions of normal blocks, tools, and other map maintainer tools.

NextGen Bedrock
StarNinjas

Adds an indestructible bedrock layer at the bottom of the world.

Lava + Water > Stone
1F616EMO

Cool Lava into technically special stones for easier cleanup

WorldEdit Wall Block
SkyBuilder1717

Adds block and item for making big structures easily as possible.

doorbell
Miniontoby

A doorbell mod with sound

Fly-B-Gone!
Hugues Ross

Hides butterflies/fireflies

Metatool
SX

Provides API to register node metadata tools along with few useful tools

Debugging Console
sorcerykid

Provides an in-game HUD to easily monitor debug output